I. Field of the Invention
The present invention relates to sample handling apparatus and, more particularly, to apparatus for circulating sample holders in a storage compartment past an operating station. The invention is particularly well suited for handling samples which, after stabilization at the operating station, are removed from the storage compartment, operated upon, and then returned to the compartment.
II. Description of the Prior Art
U.S. Pat. No. 3,859,528 (Luitweiler et al., issued Jan. 7, 1975) illustrates a prior commercial sample handling apparatus for circulating a plurality of sample holding vials past an operating station. The vials are supported within respective compartments of multi-compartment sample holding trays and the trays are circulated in rectilinear fashion around the sample storage compartment of the apparatus. At the operation station an elevator removes a vial, positions it in a radiation detection chamber for analysis, and then returns the vial to the compartment. To this end the sample storage compartment is loaded with two longitudinally extending, generally parallel columns of trays on opposite sides of the operating station. Longitudinally movable fingers at opposite ends of each column increment the entire column of trays longitudinally a distance of one tray depth to drive trays in the first column toward the operating station and trays in the second column away from the operating station. After incrementing each column of trays, trays at the remote ends of the columns are indexed laterally from one column to the other after which the fingers again increment the columns one tray depth.
While the foregoing apparatus functions reasonably well for the purpose intended, it suffers from a number of inherent drawbacks which reduce its overall commercial attractiveness. First, because of the limited longitudinal drive capabilities of the incrementing fingers, incremental movement of each tray column requires that each tray abut an adjacent tray so that the trays can increment each other serially in domino fashion. As a result, if the apparatus does not contain a full load of trays, the incrementing fingers are unable to longitudinally increment the tray columns to positions wherein the trays at the remote ends of the columns may be laterally indexed between columns. In addition, when indexing, the apparatus may fail to accurately align a tray in position over the elevator at the operating station. In such a case the elevator, instead of engaging and removing the sample vial, will instead strike the tray and cause the apparatus to jam. Further, there is no provision in the prior apparatus for detecting or signalling the occurrence of the foregoing malfunctions.
In copending U.S. application Ser. No. 754,815, now abandoned for "Sample Handling Apparatus" filed concurrently herewith in the name of Richard S. Kampf, a novel sample handling apparatus is disclosed which is capable of circulating any number of sample holders from one to a full load. The apparatus also is capable of accurately stabilizing each holder as it moves to and away from and while at an operating station. To these ends, the apparatus includes first and second parallel conveyor means or opposite sides of the operating station for conveying sample holders in first and second opposite directions toward and away from the station. Means are also included at the remote end of each conveyor for halting motion of the sample holders in first and second longitudinal stop positions for subsequent lateral movement of the end-most sample holders between the conveyors. During such lateral movement, one of the holders is moved into position at the operating station and indexing means is provided for then engaging and stabilizing the holder during operation of the station.
While the apparatus of the copending application is a substantial improvement over prior apparatus, even it may be subjected to operating problems. For example, it is possible in the apparatus for a sample holder on a conveyor not to fully seat in its longitudinal stop position for subsequent lateral movement by lateral drive means. If such occurs, the holder and lateral drive means may be misaligned, and the lateral drive means may improperly engage and tip over or otherwise disturb the position of the holder. Also, in the apparatus, the operating station is capable of operating when the indexing means is not fully engaged with a sample holder at the station. If such operation occurs, it is possible that the station may jam or otherwise disturb the position of the holder in an undesirable manner.
In addition to overcoming the foregoing possible problems, it is, of course, desirable that such a sample handling apparatus include improved means for increasing the speed with which samples may be transported for processing while maintaining the stable transport thereof.